Heating systems used in warehouses or similar large volume commercial settings typically include a series of tubular heating members suspended from the ceiling, with a heating unit comprising a gas-fired combustion chamber forcing hot air through the system to provide heat. One such heating system is shown in U.S. Pat. No. 4,319,125, issued Mar. 9, 1982, to Prince, which is incorporated herein by reference. In large buildings, it is sometimes necessary to install two or more heating units in order to adequately raise the temperature of the working environment to a comfortable level. In such applications, multiple units may be operated at different levels and on different time schedules depending upon the area to be warmed by each individual unit.
Typically, each individual heating unit in a multiple unit setting has its own exhaust vent through which combustion gases are allowed to vent to the outdoors. Heating units of this type may rely on natural draft ventilation, or may include a forced draft ventilation system wherein a fan is employed to improve air flow through the exhaust vent, thereby improving the effectiveness of the vent in removing unwanted combustion gases. Natural draft ventilation systems typically vent through the ceiling of the building, while forced draft systems may utilize either vertical vent pipes extending through the ceiling, or horizontal vent pipes extending through a wall.
The use of multiple heating units in a single building typically requires a separate exhaust vent for each unit, necessitating a plurality of holes through either the ceiling or walls. This is highly undesirable for a number of reasons, not the least of which is the expense involved in cutting multiple holes in the ceiling and/or walls of a building. Accordingly, a need has been recognized for a way to effectively vent exhaust gases from a plurality of heating units through a single opening.
Solutions to the problems associated with multiple vent openings have been attempted in connection with systems other than a radiant tube heater system as addressed herein. For example, U.S. Pat. Nos. 1,484,328, issued Feb. 19, 1924, to Heimbach, 4,187,833 issued Feb. 12, 1990, to Zahora, et al., and 4,979,343 to Baccelliere, each discloses a chimney or flue stack which provides a common exhaust pathway for multiple fuel fired units. None of the systems disclosed in these patents has been found acceptable for use with radiant tube heating systems, particularly when forced draft heating units are employed. With multiple forced draft heating units, it is necessary for each exhaust vent to have an independent flow path to allow effective operation of multiple units at different times and/or heating rates. Accordingly, a need has also been recognized for a multiple unit exhaust vent adapted for use with forced draft heating units.